Tony Leung: 'The others thought I was playing a character, but actually I was living behind the character' Photo: AP

Traditionally, Hong Kong cinema has exported martial-arts skills, tough-guy personas and the ability to leap from tall buildings in a single take - but its actors are only rarely in demand for their acting. When it comes to standing still and giving a dramatic performance, Tony Leung Chiu-wai is practically the only name on the list.

Leung is one of the few Hong Kong actors to have won an international acting prize (best actor at Cannes for Wong Kar-wai's In the Mood for Love), and it's an exceptional year when he doesn't win something at the national film awards. He has been called Hong Kong's answer to Johnny Depp, partly because of his adoring female fans and age-proof pin-up looks (he's 41), but also for his ability to switch between small art films and big commercial ones without missing a step. As well as Wong Kar-wai, he has worked with other high-end Asian directors - China's Zhang Yimou, Taiwan's Hou Hsiao-hsien, Vietnam's Tran Anh Hung - and has starred in local hits such as John Woo's Hard Boiled and suspense thriller Infernal Affairs, which was Hong Kong's biggest box office hit of 2002 and is due for UK release this week.

But where Depp is the lovable eccentric, Leung is the tragic hero - solitary, sensitive and vulnerable. He has a way of conveying suppressed emotion, with furrowed brow and eyes welling with tears, that makes women want to take him home and look after him, and men want to emulate him.

"Once I'm committed to a role, I will go very deep into it, even when I'm not at work," he says. "I'll keep on studying the script, maybe 40 or 50 times. I might call a scriptwriter at three in the morning to say I've thought of something new."

That's when there is a script. Much of Leung's best work has been with Wong Kar-wai, who prefers to feel his way towards a story through improvisation and experimentation. "You always need to see the finished movie," Leung says of his five films with Wong, "because when you are doing it you don't have any idea what the story is about. You can play the character one way, then play him a different way the next day. Or maybe, after three months' shooting, he'll tell you, 'This is not the character we want. Maybe we'll change it.' Or, 'The story is totally different now.' It's very interesting."

A prime example is Happy Together, from 1997, in which Leung and Leslie Cheung played gay lovers in Buenos Aires. Cheung, who tragically committed suicide last year, was just coming out as gay when the film was released, but Leung has had a well-publicised relationship with actress Carina Lau for the past 10 years. Few local actors would have taken such a risky role, especially because in Hong Kong, homosexuality was decriminalised only in 1990.

Wong didn't persuade Leung to play the role; he tricked him. "He gave me a fake script," Leung laughs. "Originally my character wasn't gay - his father was. In my script, the father dies in Argentina and I go there and find out he had a lover, who is Leslie. So we go to Argentina and we spend six weeks learning Spanish and the tango. And after that, Kar-wai says, 'I think it would be much more interesting if your role is gay.' I was surprised, but not angry. We start shooting the next day - and the first scene is a love scene."

Leung is now finishing his sixth film with Wong, titled 2046. It is their most ambitious project to date, set partly in the future (hence the title) and partly in the 1960s. Leung and his co-star Maggie Cheung reprise their characters from In the Mood for Love, a 1960s couple who almost fall into a love affair when they discover that their spouses are doing the same. This explains the slightly incongruous Clark Gable moustache he is sporting. Other than that he looks relaxed, but he claims to be exhausted, having been shooting 2046 for four years, on and off.

"Near the end of every movie with Kar-wai I tell him I'm running out of energy. It never gets any easier. But this film will look darker, and meaner and cooler. And this time I have a lot of love scenes. I hope my ass looks as good as my face!"

Infernal Affairs, by contrast, is a classic Hong Kong cop thriller, full of suspense and surprises, and shot to a meticulously planned schedule in 30 days. Leung plays an undercover cop in a Triad gang, while his nemesis, played by Andy Lau, is an undercover Triad among the cops. Leung was given the freedom to make changes to the character and the script; he changed several scenes, dispensing with a cliched "Let's drop our guns and duke it out" ending in favour of something more simple and elegiac. "I wanted to take a different approach. I wanted this character to be very optimistic, always with a smile on his face, but I just wasn't able to put it into the scenes. I don't know why." In other words, it's another tragic hero role.

When asked about the origins of his mournfulness, his face takes on that sorrowful expression so familiar from his films. "Maybe it's because I came from a broken home," he says. "I wasn't so happy in my childhood. My parents broke up when I was six. Before, I was a very active, naughty child, but after my father left me I stopped talking. I became very good at hiding my emotions. I felt so ashamed of telling others that I didn't have a father, because that was not common in the 1960s. People didn't break up - even if they didn't love each other - in traditional Chinese families. Not like today."

At 19 he enrolled in a year-long actors' training course with local television company TVB. "I found a way to express myself. The others thought I was playing a character, but actually I was living behind the character. I could release my emotions, and the others didn't know that was me. That's the reason I love acting so much. I wasn't asking for fame or money - it was the natural high I got addicted to."

He gained popularity as a television star, primarily in comedy roles. Film offers soon came along, but Leung waited until he was ready. He had recognised the gulf between local television and the foreign films he loved. Alain Delon, his mother's favourite, was an early role model. Then there were Robert De Niro and Al Pacino.

Nevertheless, Leung has no Hollywood ambitions himself, he says. Offers come his way from the US, Europe and Australia, but nothing has felt quite right. "If Scorsese called me up, though, I would say yes - no matter what." Which is ironic, because Scorsese has recently been earmarked to direct a Hollywood remake of Infernal Affairs. According to reports, Warner Bros have bought the rights for $1.75m via Brad Pitt's production company. Pitt is expected to play Leung's role. Meanwhile, Infernal Affairs 3 is already on its DVD release in Hong Kong, again starring Leung, who skipped part two.

Life in Hong Kong is no longer straightforward for Leung. "If I want to experience the life of an ordinary person, I cannot do it in Asia," he says. He is too recognisable to move about easily. He seldom goes out at night, and spends most of his time at home or on his boat. He loves waterskiing, or simply driving out to a deserted bay to study scripts in peace.

He is thinking of buying a home abroad. But on the other hand, he is booked up for the next three years. After 2046, which it is hoped will premiere at Cannes this year, he and Wong Kar-wai have another project on the cards. "It's going to be an action movie, with kung-fu," he reveals. "Which will be very exhausting."

· Infernal Affairs is released on Friday

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